The present invention relates to an ejector pump including an annular nozzle slot for a pumping medium directed mainly radially outwards, an annular mixing zone situated radially outside said nozzle zone, in which mixing slot an outlet opening of at least one mainly axially directed secondary channel is situated and an annular diffuser slot situated radially outside said mixing zone.
Ejector pumps of this kind have been developed, during a long period of time, into relatively small and dependable pumps with high efficiency.
Ejector pumps of this kind have come into use especially as vacuum pumps for 50% vacuum and more, especially around 85% vacuum.
A disadvantage is, however, that they are complicated to produce. A plurality of parts have to be precision manufactured and then assembled with very small tolerances as to mutual positions as well as angular accuracies in order to achieve an ejector pump with desired characteristics. When discrepancies occur, corrections can be made by adjusting adjustable parts. This, however, requires manual work which will increase the cost of manufacturing.
Another disadvantage is that the high efficiency of ejector pumps is highly dependent on a certain, narrowly delimited pressure value. On each side of this pressure value the characteristics of the pump will be rapidly deteriorated, which is inconvenient with respect to the fact that the pressure rate in compressed air plants, in workshops, factories etc, often varies many decades of percent up and down.
The object of this invention is to achieve an improved ejector pump in which the above disadvantages are eliminated totally or to a great extent. This has been obtained, according to the invention, by giving the ejector pump the characteristic features stated in the accompanying claims.